Circuit breaker



Sept. 2, 1947. J. G. JACKSON ETAL CIRCUIT BREAKER Filed March 23, ,1942 5 Sheets-Sheet 1 6. ackson NucZZer 3, 2 BY e O T 6- AIIO Y Sept 2,1947.

J, G. JACKSON ETAL CIRCUIT BREAKER Filed. larch .25 1942 5 Sheets-Sheet 2 6. Jackson.

Z1 ,Muallet Sept; 2, 1947.

J. G. JAK$ON ET AL CIRCUIT BREAKEfi Filed larch 25, 1942 5 Sheets-Sheet 3 7 43 7 INVENTORS John G. Jacl'son ReihZoIJ flucllar.

ATTO Y Sept. 2, 194 7- J. G. JACKSON ET'AL CIRCUIT BREAKER Filed'uarcn zs, 19 12 5 Sheets-Sheet 4 dul RaznZoZ 1'30? a! Mueller ATroRNf i Sept; 2, 1947.

-J. G. JACKSON ET AL C IRCUIT BREAKER 5 Sheets-Sheet 5 Filed March 23, 1942 Insu/afion 9 Insulat/m INVENTQRS 1/0717: G Jackson ReinZoZal MucZZcr ATTO Patented Sept. 2, 1947 UNITE-D s'rArEs PATENT orrics CIRCUIT BREAKER John G. Jackson and Reinhold Mueller, Detroit, Mich, assignors to Square D Company, Detroit, Mlcln, a corporation of Michigan Application March 23, 1942, Serial No. 435,850

24 Claims. (01. 200-88) This invention relates to automatic electric circuit breakers which are manually operable to make and break the circuit therethrough and which are automatically operable upon the occurrence of predetermined current overloads to effect opening of the circuit.

One object of the invention is to provide'an improved form of manually and automatically operable electric circuit breaker mechanism.

Another object of the invention is to provide a manually and automatically operable electric circuit breaker utilizing a single operating mechanism with simplified arrangement for effecting the operation of a plurality of poles through said single mechanism, manually and automatically upon the occurrence of an overload through any one or more of the poles.

Another object of the invention is to provide a manually and automatically operable electric circuit breaker having a main operating spring, one point of force application of which is maintained substantially stationary during manual operation to effect quick make and break of the circuit breaker contacts, and in whichthe normally stationary point of force application is released upon the occurrence of a current overload to eiiect automatic opening of the circuit breaker contacts.

Another object of the invention is to provide a manually and automatically operable circuit breaker mechanism, spring operated with a snap action to on and oil positions .wherein a positive operating connection is provided between the manually operable handle and the switching member to apply a positive forceto separate the contacts in the event of sticking or welding.

Another object of the invention is to provide a manually and automatically operable circuit breaker mechanism in which an operating part is releasable upon the occurrence of a, current overload and in which separation of the circuit breaker contacts is immediately eflected upon movement of the operating part after release.

'Another object of the invention is to provide an improved and simplified form of current responsive tripping means for an automatically operable electric circuit breaker.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments of the invention in which:

Figure 1 is a plan view of a 3-pole form of circuit breaker according to the present invention with the cover removed.

Figure 2 is a vertical sectional view through the center pole of the circuit breaker upon the line IIII of Figure 1, the mechanism bein shown in the on. position.

Figure 3 is a partial view similar to Figure 2 showing the parts in manual off position.

Figure 4 is a partial view similar to Figures? and 3, but showing the parts in automatic off position. a

Figure 5 is a vertical sectional view through an outside pole of the breaker along line V--V of Figure 1.

- Figure 6 is a partial detail sectional view on the line VI-VI of Figure 2.

Figure 7 is a partial detail sectional view on the line VII-VII of Figure 2.

Figure 8 is a, partial vertical sectional view similar to Figure 2 of a slightly modified form of mechanism.

The drawings, in which like reference numerals indicate like parts, show the invention in connection with a 3-pole circuit breaker, although it will be understood that with the omission of the portions of the base and mechanism pertaining to the outside poles, the center pole and mechanism constitutes a single pole breaker and that with the omission of the conducting portions in a single pole, the device would correspond to a 2-pole breaker, one or the features of the invention being the facility with which the mechanism is thus easily adapted to single or varied multiple forms in the same or in different bases.

As illustrated in the drawing, the circuit breaker is mounted within a cutout base portion I having side walls 2 and 3 and intermediate walls 4 and 5, the walls 4 and 5 serving to divide the interior of the breaker into three individual compartments. The operating mechanism for the breaker is disposed in the middle compartment between the interior walls 4 and 5 and is mounted within a supporting U-shaped metallic bracket 6 rigidly mounted in the bottom of the base as by means of the studs 1. Supported in the opposite side walls of the bracket 6, pivot pins 8 pivotally mount arms 9, which together form the conducting switching arm for the central .pole of the breaker. The arms 9, H are bent to'provide transverse, portions I! which are rigidly secured to a transverse insulating plate I 3 by screws 30 with the conducting arms extending through the plate II! in immediate side by side relation to the contacting end where they support a movable contact H. The under surfaces of arms 9 and H adjacent the contact I4 are insulated 3 from theare "by a small insulating plate 25 mounted on the arms by an interlocking slot and flange connection.

Also pivotally mounted upon the pivot pins 8, at one end of their corners, are a pair of triangular-shaped operating links |5. Another corner of the links l5 are pivotally connected by pivots In to one end of a second pair of operating links I6 whose opposite ends pivotally engage a transverse pin H which is slidably disposed within elongated, inclined slots 18 in the conducting switching arms 9 and H. The upper portions of the side walls of bracket 6 have extensions l9 within which is pivotally mounted the operating handle 2| upon a transverse bridging pin 22, the interior portion of the operating handle being provided with a projecting arm 23 carrying a' pin 24 disposed within triangular slots 25 in the third corner of the triangular-shaped links |5. Springs 25 mounted by looped portions about the pivot pins 3 between links l5 and arms 9 and II have one of their ends anchored on the links l5 as at 21 and their opposite ends exerting a bia against pin 24 in a counterclockwise direction, as viewed in Figure 2.

Supporting projections 28, integral with the bracket 6, carry a transverse pin 29 upon which is pivoted a release lever 3|, the major portion of which is U-shaped in cross section and which supports, at a point remote from the pivot point 29, a transverse pin 32 pivotally carrying a spring link 33. An opposed spring link, formed for the sake of symmetry as a pair on the opposite sides of spring link 33, is indicated at 34 and is pivotally mounted on the pivot pin l1, this portion of the mechanism being better shown in Figures 6 and 7. The links 33, 34 have straight body portions with flanged ends 35 on the links 34 and 35 on the link 33, these links being elongated so that the flange portions of each extend adjacent the pivotal mounting of the other in the opened positions of the contacts for both manual and automatic opening, as in Figures 3 and 4. About the main body portions of the links 33, 34 is disposed a compression spring 31 having its end abutting the flanged ends 35, 35. With this arrangement, the links 33, 34 and spring 31 perform the functions of a tension spring while retaining the increased safety factor present in a compression spring. The spring 31 being of the compression type is less likely to be broken or otherwise rendered ineffective than would a comparable tension spring, and still the moving apart of the pivot pins I1 and 32, or the lengthening of the distance between the points of force applications, is accompanied by an increased biasing force of the spring 31 so that the force applying functions of the arrangement are similar to those of a, tension spring such as is shown in the modification of Figure 8, to be hereinafter described.

The opposite sides of the lever 3| are provided with short transverse flanges at 33, which flanges are engaged by two surfaces on the links It as at 39 and 4|. As shown in Figure 2 in the "on" position of the breaker, the surface 39 is immediately adjacent the flanges-or abutments 33 on the l'ever 3|. When the lever 3| is released, as will hereinafter be described, and rotates in a clockwise direction, the flange abutments 35 immediately engage the surface 33 to immediately start movement of the movable contact |4 prior to the spring 31 passing through its dead center position. The surfaces 4| engage the flanged abutments 33 in the event of contact welding 4 in manually moving to olF position to provide a positive force pry to separate any such weld which might occur. As the handle is moved in a counterclockwise direction to move the contacts "oif, should the contacts not move when the spring 31 passes through dead center, then the surfaces 4| engaging the flanged abutments 35 provide a direct positive prying action tending to move the switching arms. A compression spring 42 is provided between the lever 3| and the bottom of the base and exerts its bias to assist the movement of the lever 3| in a clockwise direction when it is released and to thus speed up the automatic operation of the mechanism.

The lever 3| terminates in a latching tip 43 adapted to be engaged and retained in inactive position by a metallic insert 44 in an insulating latch 45. The latch 45 is pivotally mounted at a mid portion within bearing members 46 received within the walls 2 and 3 of the breaker and its upper portion extends across the three compartments in the breaker through openings 41 in the walls 4 and 5. The latch 45 is biased in a counterclockwise direction into latching position by means of light springs 43 disposed between the latch and the walls 4 and 5. The bearings 43, and thus the latch, are maintained in a downward direction permitting only rotation of the latch 45 by means of engagement of the cover 4| with the bearing portions, the cover 43.being sealably attached to the base as by means of rivets or other means to sealably enclose the breaker mechanism against access, the cover 45 being provided with a suitable opening through which the handle 2| passes to an accessible exterior position.

The opposite ends of the breaker base are provided with ledges for each of the compartments within the base. Upon each of the ledges at the left hand end of the base is mounted a connector 5| as by means of spun over portions of rivets 52, studs 53 extending through the inserts 52 and supporting at their upper ends the manipulable solderless connectors indicated generally at 54 provided for the'reception of circuit conductors. The connectors or conducting supports 5| extend into each compartment by depending portions, return bent to provide the parallel portions 55 and 56, the upper ends of portion 56 being bent outwardly and again upwardly, as shown, to provide the portions 51 which have attached thereto threaded elements 58 receiving screws 59 provided with bearing portions 5| engaging rigid parts on the base to provide for bending of the portion 56 upon rotation of the screw 53 for calibration purposes.

Upon the portions 56, adjacent the loops as at 52, are rigidly secured bimetallic elements 63 with sheets of mica or other insulating material 54 disposed between the remainder of the portions 56 and bimetals 53 so as to insulate them from each other except at the point of attachment. but with the portions 56 mechanically backing up the bimetallic elements 53. ,The latch 45 is provided with three pins 55, one for each of the bimetallic elements 63 disposed in each of the poles of the breaker, and the free ends of the bimetallic elements 53 are adapted to engage the pins 65 to effect rotation of the latch in a releasing, clockwise directim upon flexing of the bimetallic elements 63 in this direction due to the passage of an overload current therethrough. The free ends of the bimetallic elements 53 are connected to their respective switching arms by means of flexible leads 55,

pairs connected to their respective switching arms, the leads being thus divided to provide for greater flexibility than would beprovided with 'a single large lead.

The walls 2, 3, 4 and 5 are provided with opposed slots in which are disposed magnetic plate elements 61 disposed between the portions 55 and 59 of the connectors 5i. U-shapedmagnetic yokes 8 9 are provided which embrace the portions 56 and the bimetallic elements '53, and are disposed adjacentthe-magnetic elements 51 so as to be attracted thereto upon the occurrence outside contacts 85 engage before the contact I4 so that the insulating plate I3 moves relative I to the arms 19, thus providing a biasfrom springs 8| on the arms 19 which, in turn, provides contact pressure at the contacts 85.

Upon end ledges at the right hand end of the base I are mounted conducting connectors 85 as by means of spun over portions of metallic inserts of a large overload ciir'rent, it being understood that the positions'ofthe plates 61 and'theyokes 68 may be reversed aridthe plates moved toward the yokes rather than the yokes toward the plates. Thej n'agnetic flux within these magnetic circuits formed by the plates and yokes is generated or induced from the passage of current principally through'the bimetals 53 which the mag- P netic circuits embrace. The yokes 98 are supported at one end of rotatable elements 89 pivotedat 1I upon integral side arms supported within opposed slots in the walls 2, 3, land 5, the upper portions of the. elements 59 being provided with adjusting screws 12' bearing'against the latching plate 45 and thus determining theair gaps between the yokes 58 and plates 51 and, hence, permitting a calibration of the current overload at which the magnetic effect will be sufficient to effect unlatching movement of the latch. Light springs 13 are mounted on the elements '69 and bear against the latch 45 adjacent its pivot point to bias the yokes 88 in a clockwise direction to their position of minimum air gap and hooks 14 on the springs 13' arereceived within notches in the latch 45 to retain the yoke assemblies loosely in their lower positions.

The insulating plate I3 extends across all three compartments of the breaker base, deep slots being provided in the Walls 4 and 5 to accommodate it. The edges of these slots are them-. selves provided with opposed, longitudinally extending slots, as at 15, and the plate I3 is provided with insulating wing portions 18 received within the slots 15 to aid in isolating the cham- 81 through which are threaded the studs 88 receiving the solderless connectors indicated generally at 89 for the reception of circuit conductors. The-connectors 86 extend inwardly *of the base as shown, and at the interior ends'support the stationary contacts 9| in position to cooperate with the three movable contacts I4, 85, 85. The walls 2, 3, 4 and 5 of the base are provided with opposite notches receiving spaced pairs of insulating plates 92 which may be, for example, of fiber or are resisting Bakelite, the plates '92 forming the inward boundary of the arc chamber about the contacts and being provided with elongated slots 93 through which the arms 19 and the contact carrying ends'of the arms 9, II extend and in which theyare freely movable, the slots 98 being only wide enough to permit the free passage of the switching arms so as to restrict "the flow of arc gases from the arc chambers into the main body portion of the breaker enclosure; plate I3 being disposed in front of these slots further inhibits the free flow of arc gases. The right hand end of the arcing chamber is closed by insulating plates 94 similar to plates 92 and similarly disposed in opposed slots in the walls 2,3, 4 and 5. Between the plates 92, 94 and between the walls 2, 3, 4 and 5 aredisposed arc suppressor structures forming no part of this invention and claimed in a copending ap-,

plication of Olav Maseng, Serial No. 435,799, filed March 23, 1942. These are suppressors are com.

bers from each other at this point and to inhibit the free flow of arc gases from one pole of the breaker to another. In the chambers formed between the walls 2 and 4 and the walls 3 and 5, the insulating plate I3 carries spring holding brackets 11 disposed above slots-18 in the plate I3. Through the slots 18 extend the outside switching arms 19 and springs 8I are provided between the brackets 11 and the arms 19 to bias the arms in a downward direction and to provide contact pressure between the outside pairs of contacts in the on position of the switch.

arms 19'carry contacts 85 cooperating with their respective stationary contacts and in the movement of the contacts to the on" position, the

posed of main body portions of U-shape disposed with the nights-95 against the plates 94 and with the opposite side walls 98 extending toward the interior of the breaker, with the bights 95 and the side wills 96 thus forming liners for the chambers proper. Supported in the side walls 96 and the bights 95 are a plurality of opposed spaced insulating plates 91 and 98, the plates,

91, 98 being spaced apart in the same plane parallel to the back of the base as shown in Figure 7 1 and the plates being spaced apart in a vertical plane as shown in Figure 2. The plates 91 are provided with projections 99 (Figure 1) having a long sloping face toward the interior of the breaker and an abrupt face toward the'right hand side, as shown, and the plates 98 have projections I9I with the abrupt face toward the breaker interior and the sloping face toward the right hand end of the breaker, the projections 99 and I9I cooperating to produce, in a plane, a formation providing a relatively large chamber portion at I92 over the cooperating contacts 9| and I4, and a second enlarged chamber I93 spaced therefrom toward the right hand end of the base with the two chamber portions I02 and I0 3 communicating by the restricted portion I04 which interconnects the chambers from one corner of the chamber I92 to the opposite corner of the chamber I03, the restricted portion I04 being thus inclined to the longitudinal axis of the chamber. The chambers and communicating portions thus defined are, of course, only in the individually spaced planes of alignment of the plates 91, 98, it being understood that the vertical spacing between the plates is unopposed beaeaaeso her liners. The U-shaped liners and plates ll, ll are formed of an insulating material such as fiber or are resisting Bakelite. The are chambers are provided with top plates I" disposed between the side walls and the mm of the liner and maintained in place by the cover ll.

Insulating plates I" are disposed in opposed slots in the walls I. I, l and 8 and are maintained therein by the cover It to seal oi! the left hand ends of the chambers of the circuit breaker. The adjusting or calibrating screws I! are sealed against access by means of an application of cement at ill.

The .operation of the breaker mechanism now be described:

The parts, as shown in Figure 2, are in the contacts engaged position; to manually move the contacts to disen a ed position the handle ii is rotated in a counterclockwise direction, as

shown. whereupon the pin 24 initially stresses spring 2| and then positively engages the end of the slots 15 to positively move the links II in a clockwise direction. This also effects movement of the links it through the pivotal connections at II. the pivots ll thus moving in a downward direction, the pin lI sliding slightly toward the right within the slot II to accommodate for the pivotal moving of the linkage, and the spring II being slightly compressed. When the pivot points III are in line with the pivots I and pin II, the links are on center and any further movement thereof is occasioned by the overcenter operating spring 31. However, this movement the pivots Ill through the center line is effected automatically when they have been moved adjacent this line by the operating handle 2i, this being caused by the reaction of the force stored in the springs 28 which effects movement of the linkage through the dead center position by the energy stored therein .and thus prevents the maintenance of the parts in a dead center position. As the pivots iii move through the center line. the force stored in spring ll acts to collapse the linkage i5, i8 and effect rotative movement of the switch arms 9 and ii in a counterclockwise direction into the position shown in Figure 3, the pin ll sliding down toward the back end of the slot I! in the movement of the parts. As the switching arms 9. ll open. they effect movement of the insulating plate I! which. in turn, eifects rotation of the outside switching plates I! also in a counterclockwise direction to open all of the poles of the breaker.

To again place the parts in contacts engaged position, the handle is rotated in a clockwise direction from the position of Figure 3, this rotating the link IS in a counterclockwise direction and straightening out the linkage IS, IS by the upward movement of the pivot points Hi, the pin i1 moving upwardly within the slot it until the pivots it again pass through the line between the pivots 8 and the pin i1 whereupon the spring 31, which has been stressed by the movement of the pin l1 away from the pin 32, extends its energy to eifect continued rotation of the linkage beyond center, whereupon its force is directed to effect movement of the switching arms 9 and II in a clockwise direction to engage the contacts. In this movement, as explained above, the contacts I! engage first to effect compression of the springs ll, thus providing for the application of contact pressure on the exterior poles of the breaker.

The automatic operation of the circuit breaker to disengage the contacts is as follows: This operation may be effected by the thermal elements upon the occurrence of a sustained moderate overload or it may be effected by the magnetic elements upon the occurrence of a very large or short circuit current or it may be effected by a combination of the forces exerted by the thermal and magnetic elements. Upon the occurrence of a sustained moderate overload through any one or all of the poles of the breaker. the affected bimetallic element 0! will become heated and will flex in a clockwise direction exerting a force on its associated pin II to rotate the latch I in a clockwise direction against the bias of the light springs ll. With this rotation the latching tip 44 will disengage the lever ll which will move upwardly under the combined actions of the spring I! and the main operating spring 31. The upward movement or clockwise rotation of the lever II effects immediate movement of the switching arms 0, ii through the engagement of the flanges II with the surfaces 3! on the link It which. through the engagement of pin II in the slot ll. cause the switching arms 0 and ii to immediately move to their open position, the outer poles also moving to this position through their mounting on the insulating plate II. the parts then assuming the automatic tripped position shown in Figure 4. To reset the breaker mechanism after an automatic opening, the handle is moved toward the oif" position of Figure 3, whereupon the pivots iii engage the lever II and, as the handle is moved and the links it rotated in a clockwise direction, the lever II is forced downwardly in a counterclockwise direction against the bias of springs 42 and 31 until the latch portion 43 is again disposed beneath the latch tip 44, whereupon the parts are reset in the normally off" position as in Figure 3. A movement of the operating handle in a clockwise direction will again effect engagement of the contacts as previously explained. Upon the occurrence of very heavy overloads. such as short circuits. and at the lower values depending upon the setting of the air gap of the magnetic circuit, sufficient force is exerted by the attraction between yoke 88 and plate 61 to effect rotation of the member 69 in a clockwise direction, applying its force through screw I2 to rotate the latch 45 in a clockwise direction to again effect unlatching of the lever 3|. It is understood. of course, that the thermal and magnetic elements are both being energized at the same time and that for many values of overload current. the tripping force will be the combined force exerted by the thermal and the magnetic tripping elements.

One feature of the invention lies in the manner of mounting and supporting the bimetallic elements 63. Upon the occasion of extremely heavy overloads, such as short circuits, the bimetal acts very quickly and the inertia of the latch 45 resisting movement of the free end of the bimetal may cause the bimetal to take a permanent set adjacent its attached end due to the initial resistance to the movement of its free end. Such a permanent set in the bimetallic element would result in changing the calibration of the breaker so that it can no longer respond to the predetermined values for which it was initially set. In the arrangement according to the present invention, a large part of the length of the bimetallic element adjacent its connection is backed up by a structural member which prevents the reverse movement of this portion of the bimetal and prevents the permanent set previously referred to. This structure is shown in Figure 2 wherein the lower portion of the bimetallic element 63 is tion 56 of the connector which portion extends immediately adjacent to a considerable part of the length of the bimetal in mechanically supporting relation, but being electrically insulated therefrom by the mica sheet 64. Ordinarily upon the occurrence of a heavy overload where the bimetallic element tends to quickly flex in a clockwise direction, the resistance offered by the latch 45 to this quick movement of the bimetallic element would cause the lower portion of the bimetallic element adjacent to its attachment S2 to be bowed toward the left with the danger of a permanent set occurring. With this construction, the critical portion of the bimetal is structurally supported and prevented from thus bowing and taking the detrimental permanent set.

While th auxiliar spring 42 has been shown biasing the lever 3| in a clockwise direction, it is understood that this spring is supplied for the purpose of speeding up the movement of the lever and the opening of the contacts, and that with the spring 42 omitted the breaker will still function on automatic opening under the bias of spring 31. Due to the acute angle of application of force of spring 31, its moment to rotate the lever 3| is rendered small, and While the speed of opening movement of the contacts relying on the spring 31 is sufficiently fast to provide for effective operation of the breaker, still it is desired to enhance this speed of movement and to render theopening movement more positive with the addition of the spring 42,

Similarly, while the flange 38 and the surfaces 39 on links IB have been provided to effect opening of the breaker contacts immediately upon movement of the lever 3|, still with the omission of the flanges and surfaces, the breaker is still operative; however, with these omitted, it is necessary for the lever 3] to move upwardly adjacent its extreme position before opening of the contacts is effected, this occurring when the spring 31 passes through the pivots Ill. Again the operation of the breaker mechanism is fully opera- I tive but the contacts will not open until the lever 3| has moved through the major portion of this opening movement. To render .the contact separation quicker, the flanges 38 and surfaces 39 are provided so that the contacts begin to open immediately the lever 3| starts to move, and not when the spring passes through center which, however, still occurs, as may be seen from an inspection of Figure 4 of the drawing, wherein the spring is passed through the pivots ID to collapse the linkage in the contact opening direction. However, actual contact opening was effected prior to this movement through center and collapse of linkage by means of the direct engagement between flanges 38 and surfaces 39 on the links Hi.

In the manual operation of the breaker, should the contacts weld together so that the spring 31 is not sufficiently strong to effect opening-thereof after the pivots 10 move through the 'line between pivots 8 and pin I], continued rotation of the handle in clockwise direction places a prying action upon the switching arms through the surfaces H on the links 16 which engage the flanges 38 to effect a positive prying action 'on the contact arms 9 and II through pin IT. This prying action will break any weld which may occur between 'the contacts, whereupon the operating springs 31 will continue the opening movement to disengaged position.

In the modification of Figure 8, the links N5 of complex form have been changed to the simple straight links I03 and the flanges 38 have been removed from the lever 3|, the similar lever in this figure being designated at I09, and pins III are provided on the links I08 which engage within slots H2 within a pair of links H3 pivoted as at I I4 on the lever I09. Also, the main operating spring arrangement of the preferred embodiment providing a compression spring has been changed to show the operationally equivalent simple tension spring H5. The operation of the breaker of Figure 8 is similar to that previously described, the links H3 and pin and slot arrangement Ill and H2 providing for the immediate movement of the contact to disengaged position when the lever I09 is released by the engagement of the end. of the slot H2 with the pin III to immeditely move the switch blades in the opening direction. The contact prying action on contact welding is similarly provided for by the engagement of the pin III in the bottom of the slot H2. The preferred embodiment, however, omits the extra parts shown in the modification by providing the proper surface engagements directly on the lever 3| and the links l6.

Whil certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims:

What is claimed is:

1. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, an operating handle manually movable into opposite stable operating positions, an operating spring having one point of force application movable and exerting its bias upon the movable contact arm and its other point of force application maintained stationary, and means for effecting snap movement of said contact arm to stable make and break positions in response to movement of said operating handle into its opposite stable operating positions and without moving the stationary point of force application of the operating spring, said spring bias determining the contact pressure while the contacts are engaged, and maintaining it regardless of the movement of the operating handle until the snap movement occurs.

2. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivoted operating handle manually oscillatable into opposite stable-operating positions, an operating spring having one point of force application movable and operating on the movable contact arm and its other point of force application normally maintained stationary, and means for effecting snap movement of said contact arm to stable make and break positions in response to movement of said operating handle into its opposite stable operating positions and without moving the stationary point of force application of the operating spring, said spring bias determining the contact pressure while the ,contacts are engaged and maintaining it regardless of the movement of the operating handle until the snap movement occurs, current responsive means latching said last mentioned point of force application in stationary position, including means for releasing said normally stacurrence of a current overload through the breaker, movement of said normally stationary point of force application effecting automatic movement of the movable contact arm to break the circuit through the breaker.

3. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkage having one end operatively connected to said movable contact arm, an operating spring havin one point of force application normally stationary and its other point of force application on said linkage, an operating handle, and means for moving the pivot point of said operating linkage through a dead center postion upon movement of said operating handle to eifect movement of the contact arm under the reaction force exerted by said operating spring without movement of said normally stationary point of force application.

4. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkage having one end pivoted to a fixed part and the opposite end pivoted to a part engaging said movable contact arm, an operating spring having one point of force application normally stationary and its other point of force application on said part on which said opposite end of said linkage is pivoted, an operating handle.

and means for moving the pivot point of said operating linkage through a dead center position upon movement of said operating handle to effect movement of the contact arm under the reaction force exerted by said operating spring without movement of said normally stationary point of force application,

5.- An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkage having one end pivoted to a part engaging said movable contact arm, an operating spring having one point of force application normally stationary and the other point of force aptionaiy point of force application upon the ocplication on said part on which said linkage is pivoted, an operating handle, and means for movin the pivot point of said operating linkage through a dead center position upon movement of said operating handle to effect movement of the contact arm under the reaction force exerted by said operating spring, and current responsive means for releasing said normally stationary point of force application upon the occurrence of an overload through the breaker to effect movement thereof and automatic movement of the contact arm to open circuit position.

6. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkag having one end pivoted to a fixed part and the opposite end pivoted toa part engaging said movable contact arm, an operating spring having one point of force application normally stationary and its other point of force application on said part on which said linkage is pivoted, said part slidably engaging said contact said operating linkage through a dead center position upon movement of said operating handle to effect movement of the contact arm under the reaction force exerted by said operating spring without movement of said normally stationary point of force application.

7. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkage having one end pivoted to a normally fixed part and the opposite end pivoted to a part engaging said movable contact arm, an operating spring having one point of force application normally stationary and its other point of force application on said part on which said linkage is pivoted, an operating handle, means connecting said handle to said linkage through a limited lost motion connection including a spring stressed during initial movement of the handle in a direction to effect movement of the linkage to open the circuit through the breaker, said last mentioned spring operating to throw the linkage through its dead center position when it has been moved adjacent thereto by the operating handle whereby maintenance of the parts in dead center position is prevented, movement of said linkage through said dead center position effecting movement of the contact arm under the reaction force of the operating spring as the linkage collapses on the op posite side of the center position.

8. An electric circuit breaker comprising a stationary contact, a movable contact arm carryin a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, an operating linkage operatively connected to said contact arm. an'operating handle connected to effect movement of said operating linkage, an operating spring connected to said linkage to exert a bias thereon, a pivoted lever, a latch for said lever, a point of force application of said operating spring Being mounted on said lever and normally held stationary by said latch, and current responsive means for effecting movement of said latch to release the lever and permit movement of said normally stationary point of force actuation. and means whereby releasing movement of said normally stationary point of force actuation effects movement of the contact arm to open circuit position. i

9. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, an operating linkage operatively connected to said contact arm. an operating handle connected to effect movement of said operating linkage, an operating spring connected to said linkage to exert a bias thereon, a pivoted lever, a latch for said lever. a point of force application of said operating spring being mounted on said lever and normally held stationary by said latch, current responsive means for effecting movement of said latch to release the lever and permit movement of said normally stationary point of force actuation, and means whereby releasing movement of said normally stationary point of force actuation effects movement or the contact arm to open circuit position, including interengaging portions on said lever and linkage providing for immediate movement of the contact arm in the opening direction upon release of the lever prior to the operating spring passing through the center point of said linkage, and an auxiliary spring exerting a biason said lever in the direction of its unlatched movement to speed up the opening movement of said contact arm.

10. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a slot in said contact arm, a pin freely slidable in said slot, a pivotally connected operating linkage pivoted at its opposite ends to a fixed part and to said pin, a manual operating handle, having an operative connection to the link pivoted tothe fixed'part, an operating spring connectedto said pin and to a normally fixed part, rotation of said operating handle effecting movement of the pivotal connection of said linkage through the line connecting the stationary link pivot andthe pin to move the linkage to opposite sides of its dead center position and effect movement of the contact arm in response to movement of the operating handle.

11. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a slot in said contact arm, a pin freely slidable in said slot, a-pivotally connected operating linkage pivoted at its opposite ends to a fixed part and to said pin, a manual operating handle having an operative connection to the link pivoted to the fixed part, an operating spring connected to said. pin and to a normally fixed part, rotation of said operating handle effecting movement of the pivotal connection of said linkage through the line connecting the stationary link pivot and the pin to move the linkage to opposite sides of its dead center position and effect movement of the contact arm in response to movement of the operating handle, a latch for said normally stationary part to which the operating spring is connected, and current responsive means for effecting movement of said latch to provide for movement of the normally stationary part and for automatic movement of the contact arm to its open circuit position.

12. An electric circuit breaker comprising a stationary contact,-a movable contact arm carrying 'a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a slot in said a contact arm, a pin freely slidable in said slot, a

pivotally connected operating linkage pivoted at its opposite ends to a fixed part and to said pin, a manual operating handle having an operative connection to the link pivoted to the fixed part, an operating spring connected to said pin and to a normally fixed part, rotation of said operating handle effecting movement of the pivotal connection of said linkage through the line connecting the stationary link pivot and the pin to move the linkage to opposite sides of its dead center position and effect movement of the contact arm in response to movement of the operating handle, a latch for said normally stationary part to which the operating spring is connected, current responsive means for effecting movement of said latch to provide for movement of the normally stationary part and for automatic movement of the contact arm to its open circuit position, an abutment surface on said normally stationary part, and a surface on the link connected to said pin disposed closely adjacent said abutment surface in the contacts engaged position of the breaker, initial movement of said normally stationary part when released effecting engagement of said abutment surface with the surface on said link to effect immediate movement of the contact arm in the opening direction prior to the operating spring gassing through the pivotal linkage connec- 13. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pivotally connected operating linkage having one end operatively connected to said movable contact arm, an operating spring having one 'pointof force said operating spring without movement of said normally stationary point of force application, and means providing a positive, force applying connection between said operating handle and contact arm in the circuit opening direction in the event the contacts do not separate under the spring force whereby any weld or sticking which may occur between the contacts may be positively broken through manipulation of the operating handle.

14. An electric circuit breaker comprising a stationary contact, a movable contact arm carrying a contact surface adapted to cooperate with said stationary contact to make and break the circuit through the breaker, a pair of pivotally connected links adapted to be collapsed on opposite sides of an extended position, one of said links being pivotally mounted on a part engaging said contact arm, an operating spring assembly including relatively movable, oppositely directed, spring guides having flanged portions engaging a compression spring with elongating movement of said spring guides, being accomplished with increase in the compressed force of said spring, one .of said spring guides being 15. In an automatic electric circuit breaker,

separable contacts and means releasable to effect automatic separation of said contacts, a latch for said releasable means, a current traversed bimetallic element rigidly mounted at one end and having its free end disposed to effect unlatching movement of said latch upon flexing of the bimetallic element in response to the passage of an overload current therethrough, a rigidly mounted conducting connector upon which the fixed end of said bimetallic element is mounted in conducting and mechanically supporting relation, a portion of said connector being disposed immediately adjacent the highexpansion side of the bimetallic element for a considerable distancefrom the point of connection of the bimetallic element thereto, said last mentioned portion of said connector being insulated from the bimetallic element while mechanically supporting the same against movement in the direction of the high expansion side whereby to prevent the formation of a permanent set in the bimetallic element by its reaction to resistance initially offered by the latch to the quick movement thereof.

16. In an automatic electric circuit breaker, separable contacts and means releasable to effect automatic separation of said contacts, a latch'for said releasable means, a current traversed bimetallic element rigidly mounted at one end and having its free end disposed to effect unlatching movement of said latch upon flexing of the bimetallic element in response to the passage of an overload current therethrough, a rigidly mounted conducting connector upon which the fixed end of said bimetallic element is mounted in conducting and mechanically supporting relation, a portion of said connector being disposed immediately adjacent the high expansion side of the bimetallic element for a considerable distance from the point of connection of the bimetallic element thereto, said last mentioned portion of said connector being insulated from the bimetallic element while mechanically supporting the same against movement in the direction of the high expansion side whereby to prevent the formation of a permanent set in the bimetallic element by its reaction to the resistance initially offered by the latch to the quick movement thereof, said portion of said connector having an extension thereon carrying an adjustable part providing for bending of the connector to adjust the normal position of the free end of the bimetallic element and hence the value of current at which unlatching is effected.

17. In an automatic electric circuit breaker, separable contacts, means releasable to effect separation of said contacts, a pivotally mounted latch, a latching surface at one side of the pivot for said latch engaging said releasable means, a current traversed bimetallic strip having a fixed and a free end with its free end disposed to apply an unlatching force to said latch upon the side of the pivot opposite the said latching surface whereby the end of the latch carrying the latching surface is moved toward the plane of the bimetallic element in moving to unlatching position. a mem" er pivoted adjacent the pivot of said latch and carrying a magnetic armature on one end and a force applying portion on the other, a field magnet energized in accordance with the current flowing through the breaker. said armature being attracted by said field magnet for movement in response to a passage of current through the breaker and applying its force upon the latch upon the same side of the latch pivot point as the bimetallic element.

18, A multipole electric circuit breaker comprising an operating mechanism including a contact arm, an operating handle, means for effecting manual movement of said arms to contacts engaged and disengaged positions in response to movement of the operating handle, and means for effecting automatic movement of said arm to contacts disengaged position in res, onse to current overload, a cross bar connected to said operating arm, a pair of spring elements mounted on said cross bar at opposite sides of said contact arm, and a pair of additional contact armsinsulated from said first contact arm and from each other, said last mentioned contact arms being connected to said cross arms for limited lost motion connection therebetween and being engaged by said spring elements to be biased to one of said spring elements, whereby contactpressure on the outside arms is maintained by the bias of said spring elements.

19. A multipole electric circuit breaker comprising an insulating base having a pair of longitudinal interior walls dividing the base into three separate compartments, a cross arm common to said three compartments; a mechanism disposed within the central compartment including manual means for effecting movement of said cross arm and means releasable for efiecting automatic movement of the cross arm, a latch for said releasable means having at least a. portion thereof common to the three compartments, a pair of spring elements carried by said cross arm adjacent the ends thereof, a pair of contact arms mounted for rotative movement and connected to said cross arm through a limited lost motion connection, with the spring elements biasing said arms to one extreme position with respect to said cross arm, stationary contacts adapted to cooperate with contact surfaces carried by said contact arms, engagement of said movable contact surfaces with said stationary contacts being accomplished by movement of said cross arm relative to said contact arms against the bias of said spring elements whereby contact pressure is maintained. and current responsive means individually connected to the respective contact arms and operative to effect unlatched movement of said latch to effect automatic opening of the contacts upon the occurrence of current overload.

20. A multipole electric circuit breaker comprising an operating mechanism including a contact arm, an operating handle, means for effecting manual movement of said arm to contacts engaged and disengaged positions in response to movement of the operating handle, and means for effecting automatic movement of said arm to contacts disengaged position in response to current overload, a cross bar connected to said operating arm, a pair of spring elements mounted on said cross bar at opposite sides of said contact arm, and a pair of additional contact arms insulated from said first contact arm and from each other, said last mentioned contact arms being connected to said cross arm for limited lost motion connection therebetween and being engaged by said spring elements to be biased to one extreme position of movement with respect to said cross arm, stationary contacts disposed to be engaged by contact surfaces carried on said contact arms. the two outside contact arms being adapted to engage their stationary contacts a small distance before engagement of the central arm with its contact, whereby engagement of the opposite arms is effected withmovement thereof relative to the cross arm against the bias of said spring elements, whereby contact pressure on the outside arms is maintained by the bias of said spring elements, said means for effecting automatic movement including a releasable means 17 v and a latch therefor, and a plurality of current responsive means individual to the contact arms and operating individually in response to current overloads therethrough to effect movement of the latch to unlatching position.

21, A multipole electric circuit breaker comprising an insulating base having a pair of longitudinal interior walls dividing the base into three separate compartments, a cross arm common to said three compartments, a mechanism disposed within the central compartment including manual means for effecting movement of said cross arm and means releasable for effecting automatic movement of the cross arm, a latch for said releasable means having at least a portion thereof common to the three compartments, a pair of spring elements carried by said cross arm adjacent the ends thereof, a pair of contact arms mounted for rotative movement and connected to said cross arm through a limited lost motion connection, with the spring elements biasing said arms to one extreme position with respect to said cross arm, stationary contacts adapted to cooperate with contact surfaces carried by said contact arms, engagement of said movable contact surfaces with said stationary contacts being accomplished b movement of said cross arm relative to said contact arms against the bias of said spring elements whereby contact pressure is maintained, and current responsive means individually connected to the respective contact arms and operative to efiect unlatched movement of said latch to effect automatic opening of the contacts upon the occurrence of current overload, notches in the under surfaces of said contact arms adjacent their ends remote from said contact surfaces, and parts mounted on said base receiving said notches to provide a pivotal mounting for the contact arms, said notches and part engagements and the connections with the cross arm constituting the sole mounting means for the contact arms.

22. A multipole circuit breaker comprising an insulating base having a pair of longitudinal interior walls dividing the base into three separate compartments, a metallic bracket having an operating mechanism and a contact arm mounted therein, said mechanism including an operating handle, means for effecting manual movement of the contact arm in response to movement of the operating handle and means releasable to effect automatic movement of the contact arm, means mounting the bracket and the parts theree on within the central compartment, a member connected to said contact arm and extending into the outside compartments, contact arms pivoted in said outside compartments and connected to said member by a spring biased, limited lost motion connection, stationary contacts cooperating with contact surfaces on said contact arms, the outside arms engaging their stationary contacts before the central contact arm and against the spring bias to effect a resilient contact pressure, a latch for said releasable means, and individual current responsive means in said compartments, each adapted to effect unlatching movement of said latch in response to the passage of an overload current therethrcugh,

23. An electric circuit breaker comprising stationary and movable contacts, a stationari'ly pivotecl operating member for effecting movement of the movable contact to engage and disengage the stationary contact, an operating handle, an operating spring having one point of force application movable and exerting its bias upon said 18 operating member and its other point of force application maintained stationary, operating mechanism movable by said operating handle to effect snap movement of said operating member to'quickly move the movable contact into and out of engagement with the stationary contact, the bias exerted by said operating spring upon the operating member when the movable contact is engaged effecting contact pressure between the cooperating contacts and maintaining such pressure during movement of the handle toward "off" position until such snap action occurs, said operating member remaining stationary duringmovement of the operating handle until initiation of the snap action.

24. An electric circuit breaker comprising stationary and movable contacts, an operating member for effecting movement of the movable contact to engage and disengage the stationary contact, an operating handle, an operating spring having one point of force application movable and exerting its bias upon said operating member and its other point, of force application maintained stationary, operating mechanism movable by said operating handle to effect snap movement of said operating member to quickly move the movable contact into and out of engagement with the stationary contact, the bias exerted by said operating spring upon the operating member when the movable contact is engaged effecting contact pressure between the cooperating contacts and maintaining such pressure during movement of the handle toward off position until such snap action occurs, said operating member remaining stationary during movement of the operating handle until initiation of the snap action, and current responsive means latching said last mentioned point of force application in stationary position, including means for releasing said nor- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,170,412 Jennings Aug. 22, 1939 2,182,864 Frank Dec. 12, 1939 1 2,184,372 Von Hoorn Dec. 26, 1939 1,724,675 Meuer et al Aug. 13, 1929 2,038,105 Hammerly Apr. 21, 1936 2,116,791 Jackson May 10, 1938 2,132,629 Jackson Oct. 11, 1938 2,160,562 Pittman et al May 30, 1939 2,285,770 Frank et al June 9, 1942 2,254,687 Koci Sept. 2, 1941 isles-is Johnson Nov. is, was 1,557,394 Anderson 3.3, 1925 1,617,040 Zimmer Feb. 8, 192? 2,306,235 Walle Dec. 22, 1942 2,046,701 Eandin -1 July 7, 1936 2,171,267 Doty Aug. 29, 1939 2,328,458 Jackson Aug. 31, 1943 2,240,189 Linde et al Apr. 29, 1941 2,199,622 Dorfman May 7, 1940 2,100,749

Randall NOV. 30. 193'! 

